Most of the world's supply of uranium currently comes from the mines.

Type: Evaluate
Boil It Down: Extracting uranium from seawater is not commercially viable until costs are reduced.
Missing Information: Factors that could make extracting uranium from seawater commercially viable.
Goal: Find the option that would help us determine whether extracting uranium from seawater can become commercially viable.

Analysis: The argument states that extracting uranium from seawater is not currently commercially viable due to its higher cost compared to the market price of uranium. To evaluate this argument, we need to find an option that would help us determine if there are factors or conditions that could make extracting uranium from seawater commercially viable in the future.

A) Yes. If the uranium in deposits on land is rapidly being depleted, it could lead to a scarcity of uranium, which in turn could drive up the market price of uranium. If the market price becomes higher than the cost of extracting uranium from seawater, then this method could become commercially viable. This option helps us evaluate the argument.

B) Whether most uranium is used near where it is mined does not provide any information about the costs or market prices involved in extracting uranium from seawater. This option does not help us evaluate the argument.

C) While technological advances that reduce the costs of extracting uranium from seawater might make this method more attractive, it does not directly address the issue of whether it would be commercially viable. The commercial viability depends on both the costs and market price of uranium. This option provides only partial information and does not help us fully evaluate the argument.

D) Knowing the total amount of uranium in seawater compared to land does not provide any information about the costs or market prices involved in extracting uranium from seawater. This option does not help us evaluate the argument.

E) Whether uranium can be extracted from freshwater at a cost similar to that of extracting it from seawater does not provide any information about the costs or market prices involved in extracting uranium from seawater. This option does not help us evaluate the argument.

Correct Answer: A

Bigger GMAT Picture:
On Evaluate questions, it's important to identify the core claim of the argument and then focus on finding an option that would help us determine if that claim is true or false. In this case, understanding whether land-based uranium resources are being depleted helps us assess if extracting uranium from seawater could become commercially viable in the future. It's also important to remember that Evaluate questions test your ability to recognize factors that could impact an argument's conclusion, even if they are not explicitly mentioned in the passage.
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Comparing the total quantity of uranium on land to the total quantity of uranium in water isn't terribly helpful -- it tells us nothing about whether a certain extraction method will be commercially viable.

Take a simple case. Imagine that it costs $120 to extract x pounds of uranium from seawater, but this quantity of uranium sells for $100 on the open market. One of two things has to happen to make it viable to extract the uranium this way. Either 1) the extraction cost goes down or 2) the selling price of uranium goes up. That's it.

Knowing that there's more uranium in water than on land (or vice versa) won't change the extraction cost, right? The cost is $120. That's not going to magically go down if someone whispers in our ear, "hey, there's lots of uranium in sea water!"

And even if it did, it wouldn't matter. The conclusion is that until the extraction cost goes down, this method isn't viable. So what would it be useful to know? Well, it would be helpful to know if the selling price of uranium is likely to go up. That's what (A) gives us. If the supply goes down, the selling price will go up.

I hope that clears things up!
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Understanding the argument -
Most uranium comes from mines.
Extracting Uranium from seawater is more expensive than the price it fetches on the market.
Therefore, until the cost of extraction comes down, the extraction from seawater is unlikely to be commercially viable.

We need to evaluate the argument, and in evaluation, we check the validity of the argument. The correct answers are framed along the lines of assumptions.
What if next year, every country is going to build nuclear power plants to generate electricity, and the mines in mines are not sufficient to cover the exponential surge in demand? The assumption is that if demand is exponentially high beyond what mines can cover, then whatever the cost of extraction is, we'll extract from the sea.

Or what happens if the mines are diminishing at a fast rate? In that case, the supply will plummet while demand is still high. So we can still extract from the sea whatever the cost is. We assume that knowing about supply is essential.

As you can see, there are many questions we can ask. We need to see out of these five options which one is the best of the lot.

Option Elimination -

(A) Whether the uranium in deposits on land is rapidly being depleted - OK. Let's take it to two extremes
1. Yes, the uranium in deposits on land is rapidly being depleted. It makes us believe less in the conclusion.
2. No, the uranium in deposits on land is not rapidly being depleted. It makes us believe more in the conclusion.

(B) Whether most uranium is used near where it is mined - doesn't matter. Distortion.

(C) Whether there are any technological advances that show promise of reducing the costs of extracting uranium from seawater - practically says what we already know from the argument. "until the cost of extracting uranium from seawater can somehow be reduced." Distortion.

(D) Whether the total amount of Uranium in seawater is significantly greater than the total amount of uranium on land - It doesn't matter. Out of scope.

(E) Whether uranium can be extracted from freshwater at a cost similar to the cost of extracting it from seawater - Out of scope.